Merge remote-tracking branch 'origin/released'

Conflicts:
	tools/plink/misc.h
	tools/plink/ssh.c
	tools/plink/sshbn.c
	tools/plink/winplink.c

1 files changed, 636 insertions, 567 deletions

diff --git a/tools/plink/portfwd.c b/tools/plink/portfwd.c
index 545dfecd4..e3e63e39a 100644
--- a/tools/plink/portfwd.c
+++ b/tools/plink/portfwd.c
@@ -1,567 +1,636 @@
-/*

- * SSH port forwarding.

- */

-

-#include <stdio.h>

-#include <stdlib.h>

-

-#include "putty.h"

-#include "ssh.h"

-

-#ifndef FALSE

-#define FALSE 0

-#endif

-#ifndef TRUE

-#define TRUE 1

-#endif

-

-struct PFwdPrivate {

-    const struct plug_function_table *fn;

-    /* the above variable absolutely *must* be the first in this structure */

-    void *c;			       /* (channel) data used by ssh.c */

-    void *backhandle;		       /* instance of SSH backend itself */

-    /* Note that backhandle need not be filled in if c is non-NULL */

-    Socket s;

-    int throttled, throttle_override;

-    int ready;

-    /*

-     * `dynamic' does double duty. It's set to 0 for an ordinary

-     * forwarded port, and nonzero for SOCKS-style dynamic port

-     * forwarding; but it also represents the state of the SOCKS

-     * exchange.

-     */

-    int dynamic;

-    /*

-     * `hostname' and `port' are the real hostname and port, once

-     * we know what we're connecting to; they're unused for this

-     * purpose while conducting a local SOCKS exchange, which means

-     * we can also use them as a buffer and pointer for reading

-     * data from the SOCKS client.

-     */

-    char hostname[256+8];

-    int port;

-    /*

-     * When doing dynamic port forwarding, we can receive

-     * connection data before we are actually able to send it; so

-     * we may have to temporarily hold some in a dynamically

-     * allocated buffer here.

-     */

-    void *buffer;

-    int buflen;

-};

-

-static void pfd_log(Plug plug, int type, SockAddr addr, int port,

-		    const char *error_msg, int error_code)

-{

-    /* we have to dump these since we have no interface to logging.c */

-}

-

-static int pfd_closing(Plug plug, const char *error_msg, int error_code,

-		       int calling_back)

-{

-    struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;

-

-    if (error_msg) {

-        /*

-         * Socket error. Slam the connection instantly shut.

-         */

-        sshfwd_unclean_close(pr->c);

-    } else {

-        /*

-         * Ordinary EOF received on socket. Send an EOF on the SSH

-         * channel.

-         */

-        if (pr->c)

-            sshfwd_write_eof(pr->c);

-    }

-

-    return 1;

-}

-

-static int pfd_receive(Plug plug, int urgent, char *data, int len)

-{

-    struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;

-    if (pr->dynamic) {

-	while (len--) {

-	    /*

-	     * Throughout SOCKS negotiation, "hostname" is re-used as a

-	     * random protocol buffer with "port" storing the length.

-	     */ 

-	    if (pr->port >= lenof(pr->hostname)) {

-		/* Request too long. */

-		if ((pr->dynamic >> 12) == 4) {

-		    /* Send back a SOCKS 4 error before closing. */

-		    char data[8];

-		    memset(data, 0, sizeof(data));

-		    data[1] = 91;      /* generic `request rejected' */

-		    sk_write(pr->s, data, 8);

-		}

-		pfd_close(pr->s);

-		return 1;

-	    }

-	    pr->hostname[pr->port++] = *data++;

-

-	    /*

-	     * Now check what's in the buffer to see if it's a

-	     * valid and complete message in the SOCKS exchange.

-	     */

-	    if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 4) &&

-		pr->hostname[0] == 4) {

-		/*

-		 * SOCKS 4.

-		 */

-		if (pr->dynamic == 1)

-		    pr->dynamic = 0x4000;

-		if (pr->port < 2) continue;/* don't have command code yet */

-		if (pr->hostname[1] != 1) {

-		    /* Not CONNECT. */

-		    /* Send back a SOCKS 4 error before closing. */

-		    char data[8];

-		    memset(data, 0, sizeof(data));

-		    data[1] = 91;      /* generic `request rejected' */

-		    sk_write(pr->s, data, 8);

-		    pfd_close(pr->s);

-		    return 1;

-		}

-		if (pr->port <= 8) continue; /* haven't started user/hostname */

-		if (pr->hostname[pr->port-1] != 0)

-		    continue;	       /* haven't _finished_ user/hostname */

-		/*

-		 * Now we have a full SOCKS 4 request. Check it to

-		 * see if it's a SOCKS 4A request.

-		 */

-		if (pr->hostname[4] == 0 && pr->hostname[5] == 0 &&

-		    pr->hostname[6] == 0 && pr->hostname[7] != 0) {

-		    /*

-		     * It's SOCKS 4A. So if we haven't yet

-		     * collected the host name, we should continue

-		     * waiting for data in order to do so; if we

-		     * have, we can go ahead.

-		     */

-		    int len;

-		    if (pr->dynamic == 0x4000) {

-			pr->dynamic = 0x4001;

-			pr->port = 8;      /* reset buffer to overwrite name */

-			continue;

-		    }

-		    pr->hostname[0] = 0;   /* reply version code */

-		    pr->hostname[1] = 90;   /* request granted */

-		    sk_write(pr->s, pr->hostname, 8);

-		    len= pr->port - 8;

-		    pr->port = GET_16BIT_MSB_FIRST(pr->hostname+2);

-		    memmove(pr->hostname, pr->hostname + 8, len);

-		    goto connect;

-		} else {

-		    /*

-		     * It's SOCKS 4, which means we should format

-		     * the IP address into the hostname string and

-		     * then just go.

-		     */

-		    pr->hostname[0] = 0;   /* reply version code */

-		    pr->hostname[1] = 90;   /* request granted */

-		    sk_write(pr->s, pr->hostname, 8);

-		    pr->port = GET_16BIT_MSB_FIRST(pr->hostname+2);

-		    sprintf(pr->hostname, "%d.%d.%d.%d",

-			    (unsigned char)pr->hostname[4],

-			    (unsigned char)pr->hostname[5],

-			    (unsigned char)pr->hostname[6],

-			    (unsigned char)pr->hostname[7]);

-		    goto connect;

-		}

-	    }

-

-	    if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 5) &&

-		pr->hostname[0] == 5) {

-		/*

-		 * SOCKS 5.

-		 */

-		if (pr->dynamic == 1)

-		    pr->dynamic = 0x5000;

-

-		if (pr->dynamic == 0x5000) {

-		    int i, method;

-		    char data[2];

-		    /*

-		     * We're receiving a set of method identifiers.

-		     */

-		    if (pr->port < 2) continue;/* no method count yet */

-		    if (pr->port < 2 + (unsigned char)pr->hostname[1])

-			continue;      /* no methods yet */

-		    method = 0xFF;     /* invalid */

-		    for (i = 0; i < (unsigned char)pr->hostname[1]; i++)

-			if (pr->hostname[2+i] == 0) {

-			    method = 0;/* no auth */

-			    break;

-			}

-		    data[0] = 5;

-		    data[1] = method;

-		    sk_write(pr->s, data, 2);

-		    pr->dynamic = 0x5001;

-		    pr->port = 0;      /* re-empty the buffer */

-		    continue;

-		}

-

-		if (pr->dynamic == 0x5001) {

-		    /*

-		     * We're receiving a SOCKS request.

-		     */

-		    unsigned char reply[10]; /* SOCKS5 atyp=1 reply */

-		    int atype, alen = 0;

-

-		    /*

-		     * Pre-fill reply packet.

-		     * In all cases, we set BND.{HOST,ADDR} to 0.0.0.0:0

-		     * (atyp=1) in the reply; if we succeed, we don't know

-		     * the right answers, and if we fail, they should be

-		     * ignored.

-		     */

-		    memset(reply, 0, lenof(reply));

-		    reply[0] = 5; /* VER */

-		    reply[3] = 1; /* ATYP = 1 (IPv4, 0.0.0.0:0) */

-

-		    if (pr->port < 6) continue;

-		    atype = (unsigned char)pr->hostname[3];

-		    if (atype == 1)    /* IPv4 address */

-			alen = 4;

-		    if (atype == 4)    /* IPv6 address */

-			alen = 16;

-		    if (atype == 3)    /* domain name has leading length */

-			alen = 1 + (unsigned char)pr->hostname[4];

-		    if (pr->port < 6 + alen) continue;

-		    if (pr->hostname[1] != 1 || pr->hostname[2] != 0) {

-			/* Not CONNECT or reserved field nonzero - error */

-			reply[1] = 1;	/* generic failure */

-			sk_write(pr->s, (char *) reply, lenof(reply));

-			pfd_close(pr->s);

-			return 1;

-		    }

-		    /*

-		     * Now we have a viable connect request. Switch

-		     * on atype.

-		     */

-		    pr->port = GET_16BIT_MSB_FIRST(pr->hostname+4+alen);

-		    if (atype == 1) {

-			/* REP=0 (success) already */

-			sk_write(pr->s, (char *) reply, lenof(reply));

-			sprintf(pr->hostname, "%d.%d.%d.%d",

-				(unsigned char)pr->hostname[4],

-				(unsigned char)pr->hostname[5],

-				(unsigned char)pr->hostname[6],

-				(unsigned char)pr->hostname[7]);

-			goto connect;

-		    } else if (atype == 3) {

-			/* REP=0 (success) already */

-			sk_write(pr->s, (char *) reply, lenof(reply));

-			memmove(pr->hostname, pr->hostname + 5, alen-1);

-			pr->hostname[alen-1] = '\0';

-			goto connect;

-		    } else {

-			/*

-			 * Unknown address type. (FIXME: support IPv6!)

-			 */

-			reply[1] = 8;	/* atype not supported */

-			sk_write(pr->s, (char *) reply, lenof(reply));

-			pfd_close(pr->s);

-			return 1;

-		    }

-		}

-	    }

-

-	    /*

-	     * If we get here without either having done `continue'

-	     * or `goto connect', it must be because there is no

-	     * sensible interpretation of what's in our buffer. So

-	     * close the connection rudely.

-	     */

-	    pfd_close(pr->s);

-	    return 1;

-	}

-	return 1;

-

-	/*

-	 * We come here when we're ready to make an actual

-	 * connection.

-	 */

-	connect:

-

-	/*

-	 * Freeze the socket until the SSH server confirms the

-	 * connection.

-	 */

-	sk_set_frozen(pr->s, 1);

-

-	pr->c = new_sock_channel(pr->backhandle, pr->s);

-	if (pr->c == NULL) {

-	    pfd_close(pr->s);

-	    return 1;

-	} else {

-	    /* asks to forward to the specified host/port for this */

-	    ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");

-	}

-	pr->dynamic = 0;

-

-	/*

-	 * If there's any data remaining in our current buffer,

-	 * save it to be sent on pfd_confirm().

-	 */

-	if (len > 0) {

-	    pr->buffer = snewn(len, char);

-	    memcpy(pr->buffer, data, len);

-	    pr->buflen = len;

-	}

-    }

-    if (pr->ready) {

-	if (sshfwd_write(pr->c, data, len) > 0) {

-	    pr->throttled = 1;

-	    sk_set_frozen(pr->s, 1);

-	}

-    }

-    return 1;

-}

-

-static void pfd_sent(Plug plug, int bufsize)

-{

-    struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;

-

-    if (pr->c)

-	sshfwd_unthrottle(pr->c, bufsize);

-}

-

-/*

- * Called when receiving a PORT OPEN from the server

- */

-const char *pfd_newconnect(Socket *s, char *hostname, int port,

-			   void *c, Conf *conf, int addressfamily)

-{

-    static const struct plug_function_table fn_table = {

-	pfd_log,

-	pfd_closing,

-	pfd_receive,

-	pfd_sent,

-	NULL

-    };

-

-    SockAddr addr;

-    const char *err;

-    char *dummy_realhost;

-    struct PFwdPrivate *pr;

-

-    /*

-     * Try to find host.

-     */

-    addr = name_lookup(hostname, port, &dummy_realhost, conf, addressfamily);

-    if ((err = sk_addr_error(addr)) != NULL) {

-	sk_addr_free(addr);

-	return err;

-    }

-

-    /*

-     * Open socket.

-     */

-    pr = snew(struct PFwdPrivate);

-    pr->buffer = NULL;

-    pr->fn = &fn_table;

-    pr->throttled = pr->throttle_override = 0;

-    pr->ready = 1;

-    pr->c = c;

-    pr->backhandle = NULL;	       /* we shouldn't need this */

-    pr->dynamic = 0;

-

-    pr->s = *s = new_connection(addr, dummy_realhost, port,

-				0, 1, 0, 0, (Plug) pr, conf);

-    if ((err = sk_socket_error(*s)) != NULL) {

-	sfree(pr);

-	return err;

-    }

-

-    sk_set_private_ptr(*s, pr);

-    return NULL;

-}

-

-/*

- called when someone connects to the local port

- */

-

-static int pfd_accepting(Plug p, OSSocket sock)

-{

-    static const struct plug_function_table fn_table = {

-	pfd_log,

-	pfd_closing,

-	pfd_receive,

-	pfd_sent,

-	NULL

-    };

-    struct PFwdPrivate *pr, *org;

-    Socket s;

-    const char *err;

-

-    org = (struct PFwdPrivate *)p;

-    pr = snew(struct PFwdPrivate);

-    pr->buffer = NULL;

-    pr->fn = &fn_table;

-

-    pr->c = NULL;

-    pr->backhandle = org->backhandle;

-

-    pr->s = s = sk_register(sock, (Plug) pr);

-    if ((err = sk_socket_error(s)) != NULL) {

-	sfree(pr);

-	return err != NULL;

-    }

-

-    sk_set_private_ptr(s, pr);

-

-    pr->throttled = pr->throttle_override = 0;

-    pr->ready = 0;

-

-    if (org->dynamic) {

-	pr->dynamic = 1;

-	pr->port = 0;		       /* "hostname" buffer is so far empty */

-	sk_set_frozen(s, 0);	       /* we want to receive SOCKS _now_! */

-    } else {

-	pr->dynamic = 0;

-	strcpy(pr->hostname, org->hostname);

-	pr->port = org->port;	

-	pr->c = new_sock_channel(org->backhandle, s);

-

-	if (pr->c == NULL) {

-	    sfree(pr);

-	    return 1;

-	} else {

-	    /* asks to forward to the specified host/port for this */

-	    ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");

-	}

-    }

-

-    return 0;

-}

-

-

-/* Add a new forwarding from port -> desthost:destport

- sets up a listener on the local machine on (srcaddr:)port

- */

-const char *pfd_addforward(char *desthost, int destport, char *srcaddr,

-			   int port, void *backhandle, Conf *conf,

-			   void **sockdata, int address_family)

-{

-    static const struct plug_function_table fn_table = {

-	pfd_log,

-	pfd_closing,

-	pfd_receive,		       /* should not happen... */

-	pfd_sent,		       /* also should not happen */

-	pfd_accepting

-    };

-

-    const char *err;

-    struct PFwdPrivate *pr;

-    Socket s;

-

-    /*

-     * Open socket.

-     */

-    pr = snew(struct PFwdPrivate);

-    pr->buffer = NULL;

-    pr->fn = &fn_table;

-    pr->c = NULL;

-    if (desthost) {

-	strcpy(pr->hostname, desthost);

-	pr->port = destport;

-	pr->dynamic = 0;

-    } else

-	pr->dynamic = 1;

-    pr->throttled = pr->throttle_override = 0;

-    pr->ready = 0;

-    pr->backhandle = backhandle;

-

-    pr->s = s = new_listener(srcaddr, port, (Plug) pr,

-			     !conf_get_int(conf, CONF_lport_acceptall),

-			     conf, address_family);

-    if ((err = sk_socket_error(s)) != NULL) {

-	sfree(pr);

-	return err;

-    }

-

-    sk_set_private_ptr(s, pr);

-

-    *sockdata = (void *)s;

-

-    return NULL;

-}

-

-void pfd_close(Socket s)

-{

-    struct PFwdPrivate *pr;

-

-    if (!s)

-	return;

-

-    pr = (struct PFwdPrivate *) sk_get_private_ptr(s);

-

-    sfree(pr->buffer);

-    sfree(pr);

-

-    sk_close(s);

-}

-

-/*

- * Terminate a listener.

- */

-void pfd_terminate(void *sv)

-{

-    pfd_close((Socket)sv);

-}

-

-void pfd_unthrottle(Socket s)

-{

-    struct PFwdPrivate *pr;

-    if (!s)

-	return;

-    pr = (struct PFwdPrivate *) sk_get_private_ptr(s);

-

-    pr->throttled = 0;

-    sk_set_frozen(s, pr->throttled || pr->throttle_override);

-}

-

-void pfd_override_throttle(Socket s, int enable)

-{

-    struct PFwdPrivate *pr;

-    if (!s)

-	return;

-    pr = (struct PFwdPrivate *) sk_get_private_ptr(s);

-

-    pr->throttle_override = enable;

-    sk_set_frozen(s, pr->throttled || pr->throttle_override);

-}

-

-/*

- * Called to send data down the raw connection.

- */

-int pfd_send(Socket s, char *data, int len)

-{

-    if (s == NULL)

-	return 0;

-    return sk_write(s, data, len);

-}

-

-void pfd_send_eof(Socket s)

-{

-    sk_write_eof(s);

-}

-

-void pfd_confirm(Socket s)

-{

-    struct PFwdPrivate *pr;

-

-    if (s == NULL)

-	return;

-

-    pr = (struct PFwdPrivate *) sk_get_private_ptr(s);

-    pr->ready = 1;

-    sk_set_frozen(s, 0);

-    sk_write(s, NULL, 0);

-    if (pr->buffer) {

-	sshfwd_write(pr->c, pr->buffer, pr->buflen);

-	sfree(pr->buffer);

-	pr->buffer = NULL;

-    }

-}

+/*
+ * SSH port forwarding.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "putty.h"
+#include "ssh.h"
+
+#ifndef FALSE
+#define FALSE 0
+#endif
+#ifndef TRUE
+#define TRUE 1
+#endif
+
+struct PortForwarding {
+    const struct plug_function_table *fn;
+    /* the above variable absolutely *must* be the first in this structure */
+    struct ssh_channel *c;        /* channel structure held by ssh.c */
+    void *backhandle;		       /* instance of SSH backend itself */
+    /* Note that backhandle need not be filled in if c is non-NULL */
+    Socket s;
+    int throttled, throttle_override;
+    int ready;
+    /*
+     * `dynamic' does double duty. It's set to 0 for an ordinary
+     * forwarded port, and nonzero for SOCKS-style dynamic port
+     * forwarding; but the nonzero values are also a state machine
+     * tracking where the SOCKS exchange has got to.
+     */
+    int dynamic;
+    /*
+     * `hostname' and `port' are the real hostname and port, once
+     * we know what we're connecting to.
+     */
+    char *hostname;
+    int port;
+    /*
+     * `socksbuf' is the buffer we use to accumulate a SOCKS request.
+     */
+    char *socksbuf;
+    int sockslen, sockssize;
+    /*
+     * When doing dynamic port forwarding, we can receive
+     * connection data before we are actually able to send it; so
+     * we may have to temporarily hold some in a dynamically
+     * allocated buffer here.
+     */
+    void *buffer;
+    int buflen;
+};
+
+struct PortListener {
+    const struct plug_function_table *fn;
+    /* the above variable absolutely *must* be the first in this structure */
+    void *backhandle;		       /* instance of SSH backend itself */
+    Socket s;
+    /*
+     * `dynamic' is set to 0 for an ordinary forwarded port, and
+     * nonzero for SOCKS-style dynamic port forwarding.
+     */
+    int dynamic;
+    /*
+     * `hostname' and `port' are the real hostname and port, for
+     * ordinary forwardings.
+     */
+    char *hostname;
+    int port;
+};
+
+static struct PortForwarding *new_portfwd_state(void)
+{
+    struct PortForwarding *pf = snew(struct PortForwarding);
+    pf->hostname = NULL;
+    pf->socksbuf = NULL;
+    pf->sockslen = pf->sockssize = 0;
+    pf->buffer = NULL;
+    return pf;
+}
+
+static void free_portfwd_state(struct PortForwarding *pf)
+{
+    if (!pf)
+        return;
+    sfree(pf->hostname);
+    sfree(pf->socksbuf);
+    sfree(pf->buffer);
+    sfree(pf);
+}
+
+static struct PortListener *new_portlistener_state(void)
+{
+    struct PortListener *pl = snew(struct PortListener);
+    pl->hostname = NULL;
+    return pl;
+}
+
+static void free_portlistener_state(struct PortListener *pl)
+{
+    if (!pl)
+        return;
+    sfree(pl->hostname);
+    sfree(pl);
+}
+
+static void pfd_log(Plug plug, int type, SockAddr addr, int port,
+		    const char *error_msg, int error_code)
+{
+    /* we have to dump these since we have no interface to logging.c */
+}
+
+static void pfl_log(Plug plug, int type, SockAddr addr, int port,
+		    const char *error_msg, int error_code)
+{
+    /* we have to dump these since we have no interface to logging.c */
+}
+
+static int pfd_closing(Plug plug, const char *error_msg, int error_code,
+		       int calling_back)
+{
+    struct PortForwarding *pf = (struct PortForwarding *) plug;
+
+    if (error_msg) {
+        /*
+         * Socket error. Slam the connection instantly shut.
+         */
+        if (pf->c) {
+            sshfwd_unclean_close(pf->c, error_msg);
+        } else {
+            /*
+             * We might not have an SSH channel, if a socket error
+             * occurred during SOCKS negotiation. If not, we must
+             * clean ourself up without sshfwd_unclean_close's call
+             * back to pfd_close.
+             */
+            pfd_close(pf);
+        }
+    } else {
+        /*
+         * Ordinary EOF received on socket. Send an EOF on the SSH
+         * channel.
+         */
+        if (pf->c)
+            sshfwd_write_eof(pf->c);
+    }
+
+    return 1;
+}
+
+static int pfl_closing(Plug plug, const char *error_msg, int error_code,
+		       int calling_back)
+{
+    struct PortListener *pl = (struct PortListener *) plug;
+    pfl_terminate(pl);
+    return 1;
+}
+
+static int pfd_receive(Plug plug, int urgent, char *data, int len)
+{
+    struct PortForwarding *pf = (struct PortForwarding *) plug;
+    if (pf->dynamic) {
+	while (len--) {
+	    if (pf->sockslen >= pf->sockssize) {
+                pf->sockssize = pf->sockslen * 5 / 4 + 256;
+                pf->socksbuf = sresize(pf->socksbuf, pf->sockssize, char);
+	    }
+	    pf->socksbuf[pf->sockslen++] = *data++;
+
+	    /*
+	     * Now check what's in the buffer to see if it's a
+	     * valid and complete message in the SOCKS exchange.
+	     */
+	    if ((pf->dynamic == 1 || (pf->dynamic >> 12) == 4) &&
+		pf->socksbuf[0] == 4) {
+		/*
+		 * SOCKS 4.
+		 */
+		if (pf->dynamic == 1)
+		    pf->dynamic = 0x4000;
+		if (pf->sockslen < 2)
+                    continue;        /* don't have command code yet */
+		if (pf->socksbuf[1] != 1) {
+		    /* Not CONNECT. */
+		    /* Send back a SOCKS 4 error before closing. */
+		    char data[8];
+		    memset(data, 0, sizeof(data));
+		    data[1] = 91;      /* generic `request rejected' */
+		    sk_write(pf->s, data, 8);
+		    pfd_close(pf);
+		    return 1;
+		}
+		if (pf->sockslen <= 8)
+                    continue;      /* haven't started user/hostname */
+		if (pf->socksbuf[pf->sockslen-1] != 0)
+		    continue;	       /* haven't _finished_ user/hostname */
+		/*
+		 * Now we have a full SOCKS 4 request. Check it to
+		 * see if it's a SOCKS 4A request.
+		 */
+		if (pf->socksbuf[4] == 0 && pf->socksbuf[5] == 0 &&
+		    pf->socksbuf[6] == 0 && pf->socksbuf[7] != 0) {
+		    /*
+		     * It's SOCKS 4A. So if we haven't yet
+		     * collected the host name, we should continue
+		     * waiting for data in order to do so; if we
+		     * have, we can go ahead.
+		     */
+		    int len;
+		    if (pf->dynamic == 0x4000) {
+			pf->dynamic = 0x4001;
+			pf->sockslen = 8; /* reset buffer to overwrite name */
+			continue;
+		    }
+		    pf->socksbuf[0] = 0;   /* reply version code */
+		    pf->socksbuf[1] = 90;   /* request granted */
+		    sk_write(pf->s, pf->socksbuf, 8);
+		    len = pf->sockslen - 8;
+		    pf->port = GET_16BIT_MSB_FIRST(pf->socksbuf+2);
+                    pf->hostname = snewn(len+1, char);
+                    pf->hostname[len] = '\0';
+		    memcpy(pf->hostname, pf->socksbuf + 8, len);
+		    goto connect;
+		} else {
+		    /*
+		     * It's SOCKS 4, which means we should format
+		     * the IP address into the hostname string and
+		     * then just go.
+		     */
+		    pf->socksbuf[0] = 0;   /* reply version code */
+		    pf->socksbuf[1] = 90;   /* request granted */
+		    sk_write(pf->s, pf->socksbuf, 8);
+		    pf->port = GET_16BIT_MSB_FIRST(pf->socksbuf+2);
+		    pf->hostname = dupprintf("%d.%d.%d.%d",
+                                             (unsigned char)pf->socksbuf[4],
+                                             (unsigned char)pf->socksbuf[5],
+                                             (unsigned char)pf->socksbuf[6],
+                                             (unsigned char)pf->socksbuf[7]);
+		    goto connect;
+		}
+	    }
+
+	    if ((pf->dynamic == 1 || (pf->dynamic >> 12) == 5) &&
+		pf->socksbuf[0] == 5) {
+		/*
+		 * SOCKS 5.
+		 */
+		if (pf->dynamic == 1)
+		    pf->dynamic = 0x5000;
+
+		if (pf->dynamic == 0x5000) {
+		    int i, method;
+		    char data[2];
+		    /*
+		     * We're receiving a set of method identifiers.
+		     */
+		    if (pf->sockslen < 2)
+                        continue;      /* no method count yet */
+		    if (pf->sockslen < 2 + (unsigned char)pf->socksbuf[1])
+			continue;      /* no methods yet */
+		    method = 0xFF;     /* invalid */
+		    for (i = 0; i < (unsigned char)pf->socksbuf[1]; i++)
+			if (pf->socksbuf[2+i] == 0) {
+			    method = 0;/* no auth */
+			    break;
+			}
+		    data[0] = 5;
+		    data[1] = method;
+		    sk_write(pf->s, data, 2);
+		    pf->dynamic = 0x5001;
+		    pf->sockslen = 0;      /* re-empty the buffer */
+		    continue;
+		}
+
+		if (pf->dynamic == 0x5001) {
+		    /*
+		     * We're receiving a SOCKS request.
+		     */
+		    unsigned char reply[10]; /* SOCKS5 atyp=1 reply */
+		    int atype, alen = 0;
+
+		    /*
+		     * Pre-fill reply packet.
+		     * In all cases, we set BND.{HOST,ADDR} to 0.0.0.0:0
+		     * (atyp=1) in the reply; if we succeed, we don't know
+		     * the right answers, and if we fail, they should be
+		     * ignored.
+		     */
+		    memset(reply, 0, lenof(reply));
+		    reply[0] = 5; /* VER */
+		    reply[3] = 1; /* ATYP = 1 (IPv4, 0.0.0.0:0) */
+
+		    if (pf->sockslen < 6) continue;
+		    atype = (unsigned char)pf->socksbuf[3];
+		    if (atype == 1)    /* IPv4 address */
+			alen = 4;
+		    if (atype == 4)    /* IPv6 address */
+			alen = 16;
+		    if (atype == 3)    /* domain name has leading length */
+			alen = 1 + (unsigned char)pf->socksbuf[4];
+		    if (pf->sockslen < 6 + alen) continue;
+		    if (pf->socksbuf[1] != 1 || pf->socksbuf[2] != 0) {
+			/* Not CONNECT or reserved field nonzero - error */
+			reply[1] = 1;	/* generic failure */
+			sk_write(pf->s, (char *) reply, lenof(reply));
+			pfd_close(pf);
+			return 1;
+		    }
+		    /*
+		     * Now we have a viable connect request. Switch
+		     * on atype.
+		     */
+		    pf->port = GET_16BIT_MSB_FIRST(pf->socksbuf+4+alen);
+		    if (atype == 1) {
+			/* REP=0 (success) already */
+			sk_write(pf->s, (char *) reply, lenof(reply));
+			pf->hostname = dupprintf("%d.%d.%d.%d",
+                                                 (unsigned char)pf->socksbuf[4],
+                                                 (unsigned char)pf->socksbuf[5],
+                                                 (unsigned char)pf->socksbuf[6],
+                                                 (unsigned char)pf->socksbuf[7]);
+			goto connect;
+		    } else if (atype == 3) {
+			/* REP=0 (success) already */
+			sk_write(pf->s, (char *) reply, lenof(reply));
+                        pf->hostname = snewn(alen, char);
+			pf->hostname[alen-1] = '\0';
+			memcpy(pf->hostname, pf->socksbuf + 5, alen-1);
+			goto connect;
+		    } else {
+			/*
+			 * Unknown address type. (FIXME: support IPv6!)
+			 */
+			reply[1] = 8;	/* atype not supported */
+			sk_write(pf->s, (char *) reply, lenof(reply));
+			pfd_close(pf);
+			return 1;
+		    }
+		}
+	    }
+
+	    /*
+	     * If we get here without either having done `continue'
+	     * or `goto connect', it must be because there is no
+	     * sensible interpretation of what's in our buffer. So
+	     * close the connection rudely.
+	     */
+	    pfd_close(pf);
+	    return 1;
+	}
+	return 1;
+
+	/*
+	 * We come here when we're ready to make an actual
+	 * connection.
+	 */
+	connect:
+        sfree(pf->socksbuf);
+        pf->socksbuf = NULL;
+
+	/*
+	 * Freeze the socket until the SSH server confirms the
+	 * connection.
+	 */
+	sk_set_frozen(pf->s, 1);
+
+	pf->c = new_sock_channel(pf->backhandle, pf);
+	if (pf->c == NULL) {
+	    pfd_close(pf);
+	    return 1;
+	} else {
+	    /* asks to forward to the specified host/port for this */
+	    ssh_send_port_open(pf->c, pf->hostname, pf->port, "forwarding");
+	}
+	pf->dynamic = 0;
+
+	/*
+	 * If there's any data remaining in our current buffer,
+	 * save it to be sent on pfd_confirm().
+	 */
+	if (len > 0) {
+	    pf->buffer = snewn(len, char);
+	    memcpy(pf->buffer, data, len);
+	    pf->buflen = len;
+	}
+    }
+    if (pf->ready) {
+	if (sshfwd_write(pf->c, data, len) > 0) {
+	    pf->throttled = 1;
+	    sk_set_frozen(pf->s, 1);
+	}
+    }
+    return 1;
+}
+
+static void pfd_sent(Plug plug, int bufsize)
+{
+    struct PortForwarding *pf = (struct PortForwarding *) plug;
+
+    if (pf->c)
+	sshfwd_unthrottle(pf->c, bufsize);
+}
+
+/*
+ * Called when receiving a PORT OPEN from the server to make a
+ * connection to a destination host.
+ *
+ * On success, returns NULL and fills in *pf_ret. On error, returns a
+ * dynamically allocated error message string.
+ */
+char *pfd_connect(struct PortForwarding **pf_ret, char *hostname,int port,
+                  void *c, Conf *conf, int addressfamily)
+{
+    static const struct plug_function_table fn_table = {
+	pfd_log,
+	pfd_closing,
+	pfd_receive,
+	pfd_sent,
+	NULL
+    };
+
+    SockAddr addr;
+    const char *err;
+    char *dummy_realhost;
+    struct PortForwarding *pf;
+
+    /*
+     * Try to find host.
+     */
+    addr = name_lookup(hostname, port, &dummy_realhost, conf, addressfamily);
+    if ((err = sk_addr_error(addr)) != NULL) {
+        char *err_ret = dupstr(err);
+	sk_addr_free(addr);
+        sfree(dummy_realhost);
+	return err_ret;
+    }
+
+    /*
+     * Open socket.
+     */
+    pf = *pf_ret = new_portfwd_state();
+    pf->fn = &fn_table;
+    pf->throttled = pf->throttle_override = 0;
+    pf->ready = 1;
+    pf->c = c;
+    pf->backhandle = NULL;	       /* we shouldn't need this */
+    pf->dynamic = 0;
+
+    pf->s = new_connection(addr, dummy_realhost, port,
+                           0, 1, 0, 0, (Plug) pf, conf);
+    sfree(dummy_realhost);
+    if ((err = sk_socket_error(pf->s)) != NULL) {
+        char *err_ret = dupstr(err);
+        sk_close(pf->s);
+	free_portfwd_state(pf);
+        *pf_ret = NULL;
+	return err_ret;
+    }
+
+    return NULL;
+}
+
+/*
+ called when someone connects to the local port
+ */
+
+static int pfl_accepting(Plug p, accept_fn_t constructor, accept_ctx_t ctx)
+{
+    static const struct plug_function_table fn_table = {
+	pfd_log,
+	pfd_closing,
+	pfd_receive,
+	pfd_sent,
+	NULL
+    };
+    struct PortForwarding *pf;
+    struct PortListener *pl;
+    Socket s;
+    const char *err;
+
+    pl = (struct PortListener *)p;
+    pf = new_portfwd_state();
+    pf->fn = &fn_table;
+
+    pf->c = NULL;
+    pf->backhandle = pl->backhandle;
+
+    pf->s = s = constructor(ctx, (Plug) pf);
+    if ((err = sk_socket_error(s)) != NULL) {
+	free_portfwd_state(pf);
+	return err != NULL;
+    }
+
+    pf->throttled = pf->throttle_override = 0;
+    pf->ready = 0;
+
+    if (pl->dynamic) {
+	pf->dynamic = 1;
+	pf->port = 0;		       /* "hostname" buffer is so far empty */
+	sk_set_frozen(s, 0);	       /* we want to receive SOCKS _now_! */
+    } else {
+	pf->dynamic = 0;
+	pf->hostname = dupstr(pl->hostname);
+	pf->port = pl->port;	
+	pf->c = new_sock_channel(pl->backhandle, pf);
+
+	if (pf->c == NULL) {
+	    free_portfwd_state(pf);
+	    return 1;
+	} else {
+	    /* asks to forward to the specified host/port for this */
+	    ssh_send_port_open(pf->c, pf->hostname, pf->port, "forwarding");
+	}
+    }
+
+    return 0;
+}
+
+
+/*
+ * Add a new port-forwarding listener from srcaddr:port -> desthost:destport.
+ *
+ * On success, returns NULL and fills in *pl_ret. On error, returns a
+ * dynamically allocated error message string.
+ */
+char *pfl_listen(char *desthost, int destport, char *srcaddr,
+                 int port, void *backhandle, Conf *conf,
+                 struct PortListener **pl_ret, int address_family)
+{
+    static const struct plug_function_table fn_table = {
+	pfl_log,
+	pfl_closing,
+        NULL,                          /* recv */
+        NULL,                          /* send */
+	pfl_accepting
+    };
+
+    const char *err;
+    struct PortListener *pl;
+
+    /*
+     * Open socket.
+     */
+    pl = *pl_ret = new_portlistener_state();
+    pl->fn = &fn_table;
+    if (desthost) {
+	pl->hostname = dupstr(desthost);
+	pl->port = destport;
+	pl->dynamic = 0;
+    } else
+	pl->dynamic = 1;
+    pl->backhandle = backhandle;
+
+    pl->s = new_listener(srcaddr, port, (Plug) pl,
+                         !conf_get_int(conf, CONF_lport_acceptall),
+                         conf, address_family);
+    if ((err = sk_socket_error(pl->s)) != NULL) {
+        char *err_ret = dupstr(err);
+        sk_close(pl->s);
+	free_portlistener_state(pl);
+        *pl_ret = NULL;
+	return err_ret;
+    }
+
+    return NULL;
+}
+
+void pfd_close(struct PortForwarding *pf)
+{
+    if (!pf)
+	return;
+
+    sk_close(pf->s);
+    free_portfwd_state(pf);
+}
+
+/*
+ * Terminate a listener.
+ */
+void pfl_terminate(struct PortListener *pl)
+{
+    if (!pl)
+	return;
+
+    sk_close(pl->s);
+    free_portlistener_state(pl);
+}
+
+void pfd_unthrottle(struct PortForwarding *pf)
+{
+    if (!pf)
+	return;
+
+    pf->throttled = 0;
+    sk_set_frozen(pf->s, pf->throttled || pf->throttle_override);
+}
+
+void pfd_override_throttle(struct PortForwarding *pf, int enable)
+{
+    if (!pf)
+	return;
+
+    pf->throttle_override = enable;
+    sk_set_frozen(pf->s, pf->throttled || pf->throttle_override);
+}
+
+/*
+ * Called to send data down the raw connection.
+ */
+int pfd_send(struct PortForwarding *pf, char *data, int len)
+{
+    if (pf == NULL)
+	return 0;
+    return sk_write(pf->s, data, len);
+}
+
+void pfd_send_eof(struct PortForwarding *pf)
+{
+    sk_write_eof(pf->s);
+}
+
+void pfd_confirm(struct PortForwarding *pf)
+{
+    if (pf == NULL)
+	return;
+
+    pf->ready = 1;
+    sk_set_frozen(pf->s, 0);
+    sk_write(pf->s, NULL, 0);
+    if (pf->buffer) {
+	sshfwd_write(pf->c, pf->buffer, pf->buflen);
+	sfree(pf->buffer);
+	pf->buffer = NULL;
+    }
+}